Hybrid desiccant dehumidifier

ABSTRACT

An apparatus and method to dehumidify and reheat an air stream utilizing a combination of conventional direct expansion cooling and a high capacity desiccant dehumidification rotor. Apparatus and method is configured to achieve optimum moisture removal without overcooling at minimum energy consumption. More particularly, the invention relates to an improved method of combining conventional refrigeration with desiccant dehumidification utilizing a single air stream for efficient dehumidification without the need for secondary air streams or overcooling. Moisture is removed as condensed liquid as typical of refrigeration processes however further dehumidification occurs as a result of adsorption by the desiccant dehumidification portion. Heating of the air stream with available condenser heat prevents overcooling the air. This invention combines the two technologies in a higher capacity, more efficient approach than previous methods.

FIELD OF INVENTION

This invention relates to the apparatus and method for efficiently removing moisture from a single air or gas stream with combined rotary adsorption and refrigeration technologies. More particularly, this invention relates to an improved method of combining refrigeration technology with desiccant dehumidification technology. By doing so, improved performance and efficiency over previous methods has been proven. The method allows for the use of a single air stream to accomplish the moisture removal as compared with conventional methods requiring at least two air streams. Some of the latest known methods have been approached in a single air stream, but do not incorporate the required mix of components to ensure maximum performance and efficiency without overcooling.

BACKGROUND

Apparatus for removing moisture by condensation are found in residential, commercial, and industrial environments. Typical cooling systems operate on the principle of condensing water on a cold surface to dehumidify the air. In some cases, the cooling surface and heat rejection surfaces are combined to provide dehumidification and reheat in one air stream. Dewpoints below freezing are not possible in such systems. Adsorption (Desiccant dehumidification) systems are employed when air must be produced at sub-freezing dewpoints.

Apparatus for removing moisture by means of adsorption are also found in residential, commercial, and industrial environments. Rotary desiccant dehumidification systems typically employ two or more air streams to accomplish the dehumidification process. Previous applications of desiccant dehumidifiers have also been applied using conventional cooling system components in many different configurations. Although condenser heat has been used in prior art for reactivating a rotary adsorption device, no prior art has utilized it in this unique manner by intentionally not heating the reactivation of the desiccant rotor and utilizing only a single air stream for both adsorption and de-sorption without overcooling.

As dehumidification and drying processes have matured with time and available technology, it has proven beneficial to provide a single dehumidified and heated air stream. Dehumidified air supplied at elevated temperatures has proven to improve moisture release in absorbent and adsorbent materials resulting in faster drying processes. This invention provides the necessary mix of components to provide enhanced performance and efficiency over prior art.

SUMMARY OF INVENTION

Hybrid desiccant dehumidification apparatus and method which combines cooling technology with desiccant dehumidification technology resulting in optimum moisture removal and efficiency. Improved method of selection and placement of the system components allows for sub freezing dewpoints to be supplied without freezing of the cooling coils or overcooling the air stream. Moreover, this invention combines the processes to improve the moisture removal capacity of either system on its own at a fraction of the operating cost to perform the work with conventional systems. This invention utilizes the components in such a manner as to better optimize the efficiency of each and the system as a whole.

BRIEF DESCRIPTION OF DRAWINGS

Drawing 1 illustrates the apparatus and method of the invention having a suitable casing 1. Inlet air flows through filtration device 2, the de-sorption section of desiccant rotor 3, evaporator coil 4, air moving device 5, adsorption section of desiccant rotor 3, condenser coil 6, and is discharged as supply air. Motor 7 provides precise control of desiccant rotor speed. Compressor 8 provides direct expansion refrigeration capacity. As inlet air passes through the desiccant rotor, moisture is released from the desiccant, thereby increasing the total moisture content of the air stream. The highly saturated air is then passed through an evaporator coil where moisture is condensed from the air. After leaving the evaporator coil, the air is then passed through the second portion of the dehumidification rotor where moisture is adsorbed from the air. The air is then heated by the condensing portion of the refrigeration system and exhausted as conditioned supply air. Location of the air moving device is not relevant to overall system performance or efficiency and can be located at any number of locations for convenience.

DETAILED DESCRIPTION OF THE INVENTION

A self contained hybrid desiccant dehumidification system having, an air inlet, conditioned supply air outlet, and water drain. The apparatus provides optimum component selection and configuration in a single air stream with single air moving device to accomplish improved moisture removal and energy efficiency over prior art. Inlet air passes through an inlet filter, de-sorption of the desiccant rotor, evaporator coil, air moving device, adsorption of the desiccant rotor, and condenser coil before being discharged as dehumidified and heated supply air. The air moving device may be located for most efficient equipment layout and may be located within any portion of the dehumidification unit as required with no effect on performance or system efficiency. By utilizing a properly sized evaporator coil with a high capacity desiccant rotor, latent loading on the coil is increased over conventional systems and allows higher moisture removal rates. As moisture loading is increased even under low load conditions, the evaporator coil is less likely to freeze. The desiccant further reduces moisture levels below what is possible with conventional cooling. The introduction of condenser heat into the supply air prevents over cooling and further reduces humidity levels of the supply air. Higher moisture removal rates and lower absolute humidity levels can be achieved over conventional refrigeration systems under all normal operating conditions. As incoming air is utilized for “reactivation” of the desiccant, no direct heating of the desiccant occurs as is typical for desiccant dehumidifiers. To prevent over drying, output humidity levels can be controlled as necessary by switching to humidity control mode. The humidity sensor automatically cycles compressor operation to control output moisture levels. 

1. A hybrid desiccant dehumidification apparatus and method of combining refrigeration and rotary adsorption technology comprising: a completely self contained dehumidification unit needing only electrical power input to operate a single air stream a single air moving device an evaporator coil sized for maximum moisture removal under higher than normal latent loads a single high capacity desiccant dehumidification rotor with drive mechanism to precisely control rotational speed a condenser coil designed for optimum heat rejection in reduced humidity air an internal refrigeration compressor, piping, and controls an internal humidity sensor which can be used to prevent over drying as necessary electrical operating safeties and controls
 2. Apparatus of claim 1 comprising: a housing for said apparatus an air filtration device an air moving device a high capacity rotary adsorption device a device to drive and precisely control rotation of adsorption device a high capacity refrigeration evaporator coil a refrigeration compressor a refrigeration condenser coil a humidity control device an electrical control system which operates controls, and electrically protects said apparatus
 3. Apparatus of claim 2 wherein a single air stream is utilized
 4. Apparatus of claim 3 wherein a single air moving device is utilized
 5. Apparatus of claim 2 wherein a single high capacity desiccant dehumidification rotor with precisely controlled speed to optimize performance is used
 6. Apparatus of claim 2 wherein no heat is used for reactivation of the desiccant rotor.
 7. Apparatus of claim 2 wherein a direct expansion evaporator coil sized for optimum moisture removal at higher than normal latent loads.
 8. Apparatus of claim 2 wherein moisture is removed from an air stream as condensed water
 9. Apparatus of claim 2 wherein rotary adsorption device reduces absolute moisture level below that which can be achieved with conventional refrigeration.
 10. Apparatus of claim 2 wherein a condenser coil designed for optimum heat rejection in reduced humidity air.
 11. Apparatus of claim 2 wherein overcooling is prevented by heating the discharge air with rejected heat.
 12. Apparatus of claim 2 wherein an internal compressor provides direct expansion cooling.
 13. Apparatus of claim 12 wherein compressor has safety controls and pump down operation upon shut down of apparatus.
 14. Apparatus of claim 2 where output can be at maximum capacity at all times or switched to humidity control for automatic control to prevent over drying
 15. Apparatus of claim 12 wherein humidity control feature allows for cycling the refrigeration compressor on and off automatically. 